Light valve



Oct. 15, 1935. G. E. PERREAULT LIG HT VALV E 2 Sheets-$1 1 Filed April 51 IN I/EN TO 6. E. PERREAULT CV4. Mai ATT RNEY Oct. 15, 1935. s. E,PERREAULT LIGHT VALVE Filed April 5 1934 2 Sheets-g 2 FIG. 5

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Patented b t. 15, 1935 UNITED STATES PATENT OFFICE LIGHT VALVEApplication April 5, 1934, Serial No. 719,119

4 Claims.

This invention relates to translating devices, such as light valves, andmore particularly to improvements in the supporting means for themovable elements of such devices.

A type light valve to which this invention is applicable is disclosed inU. S. Patent 1,914,186, June 13, 1933 to E. C. Wente.

In the light valve disclosed in the patent to Wente the ribbonsupporting member has cemented thereto two gold contact metal bridges towhich the ends of the ribbons are to be clamped. One of these bridges isdivided by means of insulating material. The ends of the ribbons areclamped to the supporting member and bridged by single small bars ofinsulating material which are secured to the supporting member byscrews.

Diificulty has been encountered with varying contact resistance betweenthe ribbons and the gold contact metal bridges in the light valve asshown in the patent to Wente, particularly on the divided bridge. Thedivided bridge as shownhas two gold pieces separated by a piece ofinsulating material .002 inch wide at the center line of the valve. Thesingle strip of insulated material must hold an end of one ribbon to oneside of the divided bridge and an end of the other ribbon to the otherside of the divided bridge at a distance apart approximately equal tothe width of the insulation piece separating the two portions of thedivided bridge.

It has been determined by applicant that the difficulty which producesvarying contact resistance between the valve ribbons and bridges hasbeen caused by variation in the clamping action of the single clampingunit on, the two ribbon ends. As the thickness of each valve ribbon is.0005 inch, any slight difference in the height of the gold strips whichmake up the divided bridge will cause one ribbon to be well clamped andthe other to be poorly clamped.

The improvements which are the subject of this invention have for anobject the production of a light valve ribbon supporting and clampingmeans by which a light valve ribbon may be securely clamped in properposition for efficient operation.

A feature of the invention lies in the provision of clamping means forthe ribbons on the ribbon supporting member whereby each ribbon may beclamped separately in proper spaced relation to the other and to thevalve pole piece.

In accordance with the invention there are provided two electricallyconducting clamping members pivoted to the ribbon supporting member andinsulated therefrom. The two clamping members are of such a length thatwhen located in clamping position their free ends will each positivelyclamp a ribbon to the supporting member independently of the other.Other features material 2 0.

of the invention will appear from the following specification anddrawings in which,

Fig. 1 is a perspective view in approximately actual size of theassembled light valve;

Fig. 2 is an exploded view of the light valve 5 shown in Fig. 1;

Fig. 3 is an exploded view of the ribbon supporting member shown in Fig.2;

Fig. 4 is a side view of the ribbon supporting member with the clampingmembers in closed position;

Fig. 5 is a side view of the ribbon supporting member showing the solidbridge and single clamping member; and

Fig. 6 is an enlarged View in detail of the free end of the clampingmember shown in Fig. 4.

The light valve as shown comprises two horseshoe type permanent magnetsand 2 and a unit assembly consisting of two opposed pole pieces 3 and 4and a ribbon supporting member 5. The two pole pieces 3 and 4 and thesupporting member 5 are held together as a unit assembly by means ofscrews 6 and l and aligning rods 8 and 9. A shim ID, of predeterminedthickness, is inserted between the shoulders of the pole piece 4 and thesupporting member 5 to insure the proper location of the ribbons abovethe face of pole piece 4.

The improvements which are the subject of this invention are shownclearly in Fig. 3, in which 5 is the ribbon supporting member having anaperture ll therein to receive the face of pole piece 4. Angular piecesof insulating material 12 and 13 may be secured to the member 5 orplaced thereon and held in position by means of the 5 clamping actionbetween bridge members and the supporting member 5. Contact bridgemembers I4 and I5, made of electrically conductive material, form thetwo sides of a divided bridge and are secured to member 5 by screws [6and 11, respectively. These screws are insulated from the member 5 bywashers l8 and IQ of some suitable insulating material. The members I4and 15 are divided by a small piece of insulating It will be seen thatthe members 5 I4 and 15 are insulated from the member 5 and from eachother.

The ribbon engaging surface of each bridge member is faced with stripsof gold contact metal 2| and 22. Secured to members 14 and P5 of thedivided bridge are members 23 and 24, made of electrically conductivematerial and pivotally mounted at 25 and 26, respectively. The ribbonengaging surface of the members 23 and 24' are faced with strips of goldcontact metal as shown at 21. The clamping members 23 and 24 are held inclamping position by means of screws 28 and 29, respectively. Electricalconnection to a source of sound modulated current is made at theterminals 30 and 3!. A third terminal 32 is provided g to permit thelight valve to be used in certain recording systems requiring twosourcesof electrical current at the light valve.

At the opposite edge of supporting member 5 a solid contact bridgemember 33 is secured thereto by means or" screws (not shown) similar toscrews l5 and 5?. The ribbon engaging surface of the bridge 33 is facedwith a strip of gold contact metal 34. A single clamping member 35, madeof electrically conductive material, is secured to the member 33 bymeans of screws 36 and 3?. The ribbon engaging surface of the bridge 35is faced with a strip of gold contact metal 39. Aligning pins 38 fitinto holes in the member 35 to insure correct alignment of the cut-outportions 58 and 4| in the members 33 and 35, respectively. The dividedbridge has a cutout portion as shown at 42. The purpose of these cut-outportions in the bridge members is to increase the elfective length ofthe ribbons without increasing the overall size of the light valve usedheretofore as shown in the patent to Wente.

To prevent excessive opening or movement of the ribbons and to provideadditional damping, metal strips 4G and 35 are secured to the supportingmember 5 parallel to the ribbons by means of screws 4%.

In Fig. 4 the unit assembly including the two pole pieces 3 and l andthe ribbon supporting member 5 is shown. The pivoted clamping members 23and 24 are shown in clamping position. The shoulders of the pole piece 3are grooved as shown at E5 to prevent contact between the pole piece andthe screws 29 which are included in an electrical circuit to theribbons. Projections, as shown at 55, fit into holes, as shown at 52(Fig. 2), in the horseshoe type magnets l and 2.

In Fig. 5 a solid bridge 33 and clamping member 35 are shown inassembled position on the supporting member 5.

As shown in Fig. 6 the insulation piece 2U divides the two bridgeportions 84 and I5 of the divided bridge. The gold contact metal stripson clamping members 23 and 24 are grooved as shown at 54 and 55. Theribbons are engaged and clamped to the bridges M and I5 by the portions53 and 5'! of the clamping members. By this method of clamping thecenter portions of the ribbons they are kept from warping or bending atthe edges.

As shown in Fig. 4, the grooves 58 and 59, formed by the shoulders ofmember 5 and the face of spacing members 65 and El, provides means ofmounting and centering the light valve in place in a recording device.

From the description and drawings the advantages obtainable by the useof the improved ribbon supporting member in a light valve, as shown inthe patent to Wente, will be obvious. With the use of the ribbonclamping device constructed in accordance with this invention, eachribbon may be clamped independently of the other and a difiference inthickness of the two strips of gold contact metal on the divided bridgedoes not produce unequal clamping pressure on the two ribbons. It isseen that electrical contact to the ribbons is now made on top andbottom of the ribbons which gives an effective increase of approximatelyeight times the contact area between the ribbons and the contactbridges.

Applicant does not intend to limit his invention to the specificconstruction shown and described herein but means to include othermodifications, such as, the use of the separate pivoted clamping meanson both bridges of the ribbon supporting member to separately clamp eachend of each ribbon to the bridge members. 6

What is claimed is:

1. In a light valve having a plurality of ribbons suspended therein inspaced relation, in combination, means for supporting said ribbons insaid valve, said means comprising an apertured body 10 member, bridgemeans mounted on said body member to receive the ends of .said ribbonsin adjusted spaced relation, means for clamping the ends of each ribbonto said bridge member, said means comprising a plurality of clampingarms 5 pivotally mounted at one end thereof to said bridge means, eachof said clamping arms having at the free end thereof a ribbon engagingsurface the width of which is less than the width of the ribbon engagedthereby, and means to se- 20 cure said clamping arms in clampingposition.

2. In a light valve ribbon supporting unit, in combination, an aperturedbody member, a plurality of bridge members mounted on said body memberat opposite ends of the aperture therein, 25'

said bridge members being insulated from said body member, ribbonclamping means pivotally mounted on said bridge members, and terminalmeans mounted on said bridge members whereby said bridge members andsaid clamping members 30' may be included in an electrical circuit andmeans adjacent the ribbon engaging end of said pivoted clamping meansfor adjusting the clamping pressure exerted by said clamping means onsaid ribbon. 35 3. In a light valve having a pair of conductorssuspended therein in spaced relation, in combination, means forsupporting said conductors in said valve, said means comprising anapertured body member having mounted thereon as a 40 unit structuretherewith a pair of aligned bridge members, insulating means separatingthe ends of said bridge members, means for clamping one end of eachconductor to separate bridge members on opposite sides of saidinsulating means, 45

said means comprising a pair of electrically conductive clamping armseach pivotally mounted at one end thereof to a separate bridge member ina manner to allow the free ends thereof to engage one end of eachconductor on separate bridge 50 members adjacent said insulating means.

4. In a light valve having a pair of ribbons suspended therein in spacedrelation, in combination, means for supporting said ribbons in saidlight valve, said means comprising an apertured body member, a pair ofelectrically conductive bridge members mounted on said body member as aunit structure therewith to receive the ends of said ribbons, saidbridge members being insulated from said body member and from eachother, separate means associated with each bridge member for clamping anend of one ribbon to said bridge member, said means comprisingelectrically conductive clamping arms provided with a ribbon clampingsurface at one end thereof, the

other end of each of said arms being pivotally mounted on said bridgemembers, separate adjustable means for securing each of said clampingarnis in ribbon engaging position whereby the clamping pressure exertedby said clamping arms on said ribbons may be independently adjusted.

GEORGE E. PERREAULT.

